EP2075450A1

EP2075450A1 - Exhaust gas recirculation device and vehicle

Info

Publication number: EP2075450A1
Application number: EP08022430A
Authority: EP
Inventors: Minoru Yamamoto
Original assignee: Yamaha Motor Co Ltd
Current assignee: Yamaha Motor Co Ltd
Priority date: 2007-12-26
Filing date: 2008-12-23
Publication date: 2009-07-01
Also published as: JP5283898B2; JP2009156146A

Abstract

An exhaust gas recirculation device includes: a first exhaust extraction route (EGR1) for extracting exhaust gas from engine (101) before it enters turbocharger (103) and directing it to engine intake (111); a second exhaust extraction route (EGR 2) for extracting exhaust gas that has been cooled by passing through turbocharger (103), muffler (115) and the body frame (121) and directing it to the engine intake; and valves (V1) and (V2) for controlling, based on operation conditions of the engine, a flow of exhaust gas directed to the engine intake by means of first exhaust extraction route (EGR1) and second exhaust extraction route (EGR2). Exhaust gas can be efficiently cooled.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an exhaust gas recirculation device and a vehicle, and more particularly, to an exhaust gas recirculation device and a vehicle where exhaust gas from an engine is extracted and directed to the engine intake.

Description of the Related Art

Exhaust gas recirculation (EGR) devices for extracting a portion of exhaust gas from the exhaust side of an engine of an automobile and directing it to the intake side of the engine are known. The technique uses exhaust gas to suppress combustion of fuel within the engine and thus lower combustion temperatures, thereby reducing generation of nitrogen oxides (NOx).
Figure 14 shows a configuration of a conventional EGR device.
Arrows in the drawing indicate flow paths of gas and the like within the piping. An intake manifold 111 is connected to the intake side of an engine 101, and an exhaust manifold 109 is connected to the exhaust side of the engine. A portion of exhaust gas prior to entering exhaust manifold 109 is directed, along an exhaust extraction route EGR1, through a flow rate regulation valve V1, an EGR cooler 301, and a pressure regulation valve V3 to intake manifold 111.
Coolant flows into EGR cooler 301 to lower the temperature of hot exhaust gas within exhaust extraction route EGR1.
Flow rate regulation valve V 1 controls the amount of exhaust gas extracted from the exhaust side. Pressure regulation valve V3 serves as an intake throttle and prevents backward flow of exhaust gas in exhaust extraction route EGR1.
For such an EGR device, a portion of exhaust extraction route EGR1 is incorporated within the cylinder head.
Document 1, specified below, discloses an EGR device for extracting a portion of exhaust gas from the exhaust side and recirculating it to the intake side. A water-cooling EGR cooler is mounted on the EGR pipe in its mid-flow. An air-cooling EGR cooler is disposed downstream of the water-cooling EGR cooler.
The technique in Document 1 uses heat exchange with coolant in the water-cooling EGR cooler to cool exhaust gas to be recirculated toward the intake side down to under 200 degrees Celsius and then uses heat exchange with ambient air in the air-cooling EGR cooler to cool exhaust gas to under 100 degrees Celsius in order to lower the temperature of exhaust gas to below the temperature of coolant for cooling the engine (about 80 degrees Celsius).
Document 2, specified below, discloses a start-up control device for a diesel engine.
When the diesel engine has just entered idling stop state, the temperature of air in the engine room or in the piping of the intake system including an intercooler bypass is higher than ambient temperature. The technique in Document 2 uses this condition, supplying the combustion chamber of the engine with the hot air as intake air.
Document 3, specified below, discloses an exhaust gas reflux device for introducing exhaust gas which has not been cooled by an EGR cooler (hot EGR gas) into the engine intake during cold start or low load operation in order to promote combustion, thereby reducing generation of HC, white smoke or the like.
Document 4, specified below, discloses an exhaust gas recirculation device for an engine where a heat exchanger for cooling exhaust gas is disposed along a portion of a passageway that directs exhaust gas back into the intake air.

[Document 1] Japanese Patent Laying-Open No. 2002-188526
[Document 2] Japanese Patent Laying-Open No. 2006-46199
[Document 3] Japanese Patent Laying-Open No. 11-200955
[Document 4] Japanese Patent Laying-Open No. 7-166973

The main objects of EGR are to reduce NOx in exhaust gas and to reduce fuel consumption. To achieve these objects, EGR is more effective if cooled exhaust gas is used.
The technique in Document 1, described above, uses two coolers for cooling hot exhaust gas immediately after it is exhausted from the engine, which requires a large number of components including pipes, resulting in greater cost. Further, the EGR route is complicated, resulting in difficulties in construction and maintenance.
Furthermore, lack of a bypass around the EGR cooler makes it impossible to use exhaust gas while it is hot. To reduce exhaust smoke, it is advantageous to raise the temperature of intake air flowing into the cylinder(s) during cold start of the engine, for example. Conventionally, temperatures in the cylinder(s) were raised by means of heat of the glow plug, but the technique in Document 1 always cools exhaust gas.
The technique in Document 2 has the following problem: Though the air remaining in the engine room and the intake system is hot, it is not hot enough to enable ignition without high pressures inside the cylinder(s), bringing little advantage.
More improvement in startability could be achieved when air that has been compressed within the cylinder(s) were introduced back into the cylinder(s), which would allow for higher temperature. However, the technique in Document 2 does not allow such an operation.
The technique in Document 3 allows hot exhaust gas to be introduced directly into the intake during engine start-up, without directing it through an EGR cooler. During high load period, exhaust gas that has been cooled by the EGR cooler can be introduced into the intake. However, exhaust gas can be extracted at only one location, i.e. immediately after it is exhausted from the cylinder(s). Exhaust gas at this location is so hot that a large cooler is needed to sufficiently cool it down.
Similarly, in the technique in Document 4, exhaust gas can be extracted at one location (the exhaust manifold) immediately after it is exhausted from the cylinder(s), again requiring a large cooler to sufficiently cool the exhaust gas.

SUMMARY OF THE INVENTION

The present invention was made to solve the above problems. The object of the present invention is to provide an exhaust gas recirculation device and a vehicle where exhaust gas that has been efficiently cooled can be utilized.
To achieve the above object, according to an aspect of the present invention, an exhaust gas recirculation device includes an exhaust extraction route for extracting exhaust gas from an engine and directing it to an intake of the engine, where the exhaust extraction route includes a route for cooling exhaust gas from the engine by directing it through a frame of a vehicle or through a pipe attached to a frame.
According to the above invention, extracted exhaust gas can be passed through a frame of the vehicle or through a pipe attached to a frame. The exhaust gas from the engine can be cooled either at the frame of the vehicle or at the pipe attached to the frame, so that an exhaust gas recirculation device capable of directing to the engine intake exhaust gas that has been efficiently cooled can be provided.
Preferably, the exhaust extraction route is a low temperature exhaust extraction route for extracting exhaust gas after it has exited a turbocharger and directing it to the engine intake, and the exhaust gas recirculation device further includes: a high temperature exhaust extraction route for extracting exhaust gas from the engine before it enters the turbocharger and directing it to the engine intake; and a control means for controlling, based on operation conditions of the engine, a flow of exhaust gas to be directed to the engine intake by means of the high temperature exhaust extraction route and the low temperature exhaust extraction route.
According to the above invention, exhaust gas can be extracted from the engine at different locations for the high temperature exhaust extraction route and the low temperature exhaust extraction route. This allows relatively hot exhaust gas and relatively cold exhaust gas to be directed to the engine intake. Further, the low temperature exhaust extraction route can be used for extracting exhaust gas after it has exited the turbocharger, thereby allowing exhaust gas that has been efficiently cooled to be utilized at the engine intake.
Preferably, the low temperature exhaust extraction route directs exhaust gas from the engine to an upstream of a compressor of the turbocharger, and the high temperature exhaust extraction route directs exhaust gas from the engine to a downstream of the compressor of the turbocharger.
By employing the above configuration, exhaust gas at a relatively low pressure after it has exited the turbocharger can be directed to the upstream of the compressor of the turbocharger which is at a low pressure. Further, exhaust gas at a high pressure extracted before it enters the turbocharger can be directed to the downstream of the compressor which is at a high pressure.
Preferably, the exhaust gas recirculation device further includes: a high temperature exhaust extraction route for extracting exhaust gas from the engine before it enters a muffler and directing it to the engine intake, while the low temperature exhaust extraction route is for extracting exhaust gas from the engine downstream of an extraction location of the high temperature exhaust extraction route and directing it to the engine intake; and a control means for controlling, based on operation conditions of the engine, a flow of exhaust gas to be directed to the engine intake by means of the high temperature exhaust extraction route and the low temperature exhaust extraction route.
According to the above invention, exhaust gas can be extracted from the engine at different locations for the high temperature exhaust extraction route and the low temperature exhaust extraction route. This allows relatively hot exhaust gas and relatively cold exhaust gas to be directed to the engine intake. Moreover, the low temperature exhaust extraction route can be used for directing to the engine intake exhaust gas that has been cooled by passing through a frame of the vehicle or through a pipe attached to a frame, thereby allowing exhaust gas that has been efficiently cooled to be utilized at the engine intake.
Preferably, the low temperature exhaust extraction route is an exhaust extraction route for extracting exhaust gas that has passed at least through the muffler and directing it to the engine intake.
By thus using the low temperature exhaust extraction route to extract exhaust gas that has passed at least through the muffler, exhaust gas that has been efficiently cooled can be utilized at the engine intake.
Preferably, the exhaust gas recirculation device further includes a mixing exhaust extraction route for mixing exhaust gas passing through the high temperature exhaust extraction route with exhaust gas passing through the low temperature exhaust extraction route, where the control means controls, based on operation conditions of the engine, a flow of exhaust gas in the mixing exhaust extraction route.
By thus providing a mixing exhaust extraction route for mixing exhaust gas passing through the high temperature exhaust extraction route with exhaust gas passing through the low temperature exhaust extraction route, conditions of exhaust gas directed to the engine intake can be controlled more precisely.
According to another aspect of the present invention, a vehicle includes an engine and the exhaust gas recirculation device according to any of the above connected with the engine.
According to the above invention, a vehicle can be provided where exhaust gas that has been efficiently cooled can be utilized at the engine intake.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a configuration of an exhaust gas recirculation device for a two-wheeled motor vehicle (a saddle type vehicle) according to a first embodiment of the present invention.
Figure 2 is a side view of a two-wheeled motor vehicle incorporating the exhaust gas recirculation device of Figure 1.
Figure 3 is a side view of a frame 121.
Figure 4 is a block diagram of a control circuit for the exhaust gas recirculation device of Figure 1.
Figure 5 is a flow chart showing a control process performed by the exhaust gas recirculation device during engine start-up.
Figure 6 illustrates controls in step S115 of Figure 5.
Figure 7 shows a configuration of an exhaust gas recirculation device for a two-wheeled motor vehicle according to a second embodiment of the present invention.
Figure 8 is a block diagram of a control circuit of the exhaust gas recirculation device of Figure 7.
Figure 9 illustrates a control method for the valves of the exhaust gas recirculation device according to the second embodiment.
Figure 10 is a side view of a two-wheeled motor vehicle incorporating the exhaust gas recirculation device of Figure 1 according to a third embodiment.
Figure 11 is a side view of a frame 121.
Figure 12 is a side view of a two-wheeled motor vehicle incorporating the exhaust gas recirculation device of Figure 1 according to a fourth embodiment.
Figure 13 is a side view of a frame 121.
Figure 14 shows a configuration of a conventional EGR device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below.

[Outline]

An engine including an exhaust gas recirculation device includes at least 2 (two) exhaust extraction routes. The exhaust extraction location on exhaust extraction route EGR1 is a portion thereof where exhaust gas is still hot (hot portion), for example immediately after the exhaust valve. The exhaust extraction location on exhaust extraction route EGR2 is a portion of the exhaust piping where exhaust gas is already cold (cold portion). Switching can be made between the exhaust extraction routes for use based on operation conditions of the engine.
Hot exhaust gas extracted through exhaust extraction route EGR1 is used during engine start-up, for example. Cold exhaust gas extracted through exhaust extraction route EGR2 is used during high load period, for example.
For example, the exhaust extraction location in the hot portion can be anywhere between the exhaust port and the turbocharger, while the exhaust extraction location in the cold portion can be anywhere downstream of the turbocharger.
Alternatively, the exhaust extraction location in the hot portion can be, at the latest, a location before exhaust gas enters the muffler, while the exhaust extraction location in the cold portion can be, at the earliest, a location after exhaust gas has gone through the muffler (near the exit of the muffler).
Further, exhaust extraction route EGR2 can be a route in which extracted exhaust gas is cooled by flowing through the frame of the vehicle or through a pipe attached to the frame before being directed to the engine intake.

[First Embodiment]

Figure 1 shows a configuration of an exhaust gas recirculation device for a two-wheeled motor vehicle (a saddle type vehicle) according to a first embodiment of the present invention.
Referring to the figure, the exhaust gas recirculation device includes: an engine 101 (represented by a four-cylinder diesel engine in this implementation); an air cleaner 107 for cleaning intake air; a compressor 103b contained in a turbocharger 103 for compressing intake air; an intercooler 105 for cooling compressed air; an intake manifold 111 for directing cooled air to the cylinders of the engine; an exhaust manifold 109 for gathering exhaust gas from the cylinders of engine 101; a turbine 103a contained in turbocharger 103 for rotating compressor 103b by means of exhaust gas; an exhaust pipe 113 for directing exhaust gas from turbine 103a; a muffler 115 for muffling the sound of exhaust gas; a body frame 121 of the two-wheeled motor vehicle for cooling a portion of exhaust gas from muffler 115; and an EGR cooler 123 for cooling exhaust gas that has undergone heat dissipation at frame 121.
Exhaust extraction route EGR1 is a route in which exhaust gas immediately after exiting exhaust manifold 109 (or immediately after exiting engine 101) is mixed with air that has exited intercooler 105 and will enter intake manifold 111.
Exhaust extraction route EGR2 is a route in which exhaust gas from exhaust manifold 109 is cooled in turbine 103a, exhaust pipe 113, muffler 115, frame 121 and EGR cooler 123 and is mixed with air that has exited air cleaner 107.
Further, a valve V1 is provided in mid-flow of exhaust extraction route EGR1 for regulating the flow rate of exhaust gas in exhaust extraction route EGR1, while a valve V2 is provided in mid-flow of exhaust extraction route EGR2 for regulating the flow rate of exhaust gas in exhaust extraction route EGR2.
A throttle S is provided immediately prior to the meeting of exhaust extraction route EGR1 and the pipe extending from the exit of intercooler 105 for regulating the amount of air to be directed to the engine and preventing backward flow of exhaust gas from exhaust extraction route EGR1 toward intercooler 105.
Figure 2 is a side view of a two-wheeled motor vehicle incorporating the exhaust gas recirculation device of Figure 1.
As shown, EGR cooler 123 is attached to a cowl located above a front wheel 151. EGR cooler 123 is desirably mounted on the front part of the body, for example in front of the front fork. Further, muffler 115 is mounted above back wheel 153.
Exhaust extraction route EGR1 is provided as a route for mixing exhaust gas immediately after exiting engine 101 with intake air for engine 101. Frame 121, forming a portion of exhaust extraction route EGR2, serves as the body frame of the two-wheeled motor vehicle, too.
A route 125 is provided in the middle of frame 121 for draining water and soot. It is used for letting water or soot free-fall from the lowest point of the frame in mid-flow of the EGR.
Specifically, room (small chamber) is provided at a downward (i.e. toward the surface on which the vehicle runs) bend of frame 121 for retaining exhaust gas for a while. The flow of air, when entering the small chamber, slows down. Thus, condensed water and soot are accumulated in the small chamber. The water and soot are drained to the outside through a hole of a small diameter communicating the small chamber with the outside and through route 125. This mechanism for draining condensed water and soot is similar to a drain attached to an engine silencer in terms of its structure.
Figure 3 is a side view of a frame 121.
The implementation shown uses a hollow frame 121. The dashed line in the figure indicates a partition inside the frame. Arrows indicate routes for exhaust gas.
Frame 121 includes: an exhaust gas inlet 121a for introducing exhaust gas from muffler 115 into the frame; an exhaust gas outlet 121 b for directing exhaust gas to EGR cooler 123; an exhaust gas inlet 121c for introducing exhaust gas from EGR cooler 123 into the frame; and an exhaust gas outlet 121d for directing exhaust gas to the engine.
The frame is desirably made up of an SUS (Stainless Steel) pipe(s) in order to prevent corrosion. Frames made of various materials or made using various manufacture methods, such as an iron frame or an aluminum frame, can be used as the route for exhaust gas as long as they are hollow and have corrosion control treatment applied to the inner wall of the exhaust gas passageway.
Alternatively, a portion of a frame may have a hollow passageway, which can be used as the route for exhaust gas, and heat dissipation can occur through the frame.
In the case of a cast frame that is not hollow, an exhaust gas passageway made of an SUS (Stainless Steel) pipe(s) can be fixed to the frame, the passageway being in contact with the frame, to provide a route integrated into the frame for exhaust gas. This implementation also ensures a heat dissipation area and allows exhaust gas to be cooled more efficiently than an implementation in which a pipe alone forms the route for exhaust gas. Further, fixing a pipe integrally to the frame improves the strength of the frame.
Figure 4 is a block diagram of a control circuit for the exhaust gas recirculation device of Figure 1.
To the exhaust gas recirculation device are connected: an engine control unit 201 for controlling the electrical system of the vehicle; an engine revolution sensor 203 for measuring the number of engine revolutions; an accelerator opening sensor 205 for detecting the degree of opening of the accelerator; a coolant temperature sensor 207 for detecting the temperature of the coolant; an oil temperature sensor 209 for detecting the temperature of oil; and an intake air temperature sensor 211 for detecting the temperature of intake air.
In some implementations, output of either coolant temperature sensor 207 or oil temperature sensor 209 may be used for controlling the exhaust gas recirculation device.
Engine control unit 201 can be used for controlling valve V1 that regulates the flow rate of exhaust gas in exhaust extraction route EGR1, valve V2 that regulates the flow rate of exhaust gas in exhaust extraction route EGR2, and throttle S that prevents backward flow of exhaust gas, as described above.
Figure 5 is a flow chart showing a control process performed by the exhaust gas recirculation device during engine start-up.
When the ignition key is turned to ON in step S101, it is determined whether the coolant temperature or oil temperature is not higher than 30 degrees Celsius in step S103.
If YES in step S103, valve V1 on exhaust extraction route EGR1 is fully opened and valve V2 on exhaust extraction route EGR2 is fully closed in step S105.
On the other hand, if NO in step S103, valve V1 on exhaust extraction route EGR1 is fully closed and valve V2 on exhaust extraction route EGR2 is fully opened in step S 117.
When the starter switch is turned on in step S107, the starter of the engine is rotated in step S109, thereby starting crank rotation.
In step S111, the process waits until the number of revolutions of the crank reaches a target value or becomes larger; in step S113, fuel injection is initiated, thereby starting combustion in the cylinder(s).
In step S115, the amount of fuel injection, the time period for fuel injection, the number of fuel injections, and the fuel injection pressure are changed based on sensor detection values or the like. Further, the number of engine revolutions, the degree of opening of the accelerator, the coolant temperature or oil temperature, and the intake air temperature are detected and, based on the combination of the detection values, the degree of opening of valve V1 on exhaust extraction route EGR1 and that of valve V2 on exhaust extraction route EGR2 are changed in order to switch between various modes of introduction of exhaust gas into the engine.
Figure 6 illustrates controls in step S 115 of Figure 5.
The figure shows how engine control unit 201 regulates the degree of opening of valves V 1 and V2 based on the degree of opening of the accelerator and the number of engine revolutions in the following conditions: (a) the coolant temperature or oil temperature is lower than 20 degrees Celsius (cold state); (b) the coolant temperature or oil temperature is 20 degrees Celsius or higher than 20 degrees Celsius and lower than 60 degrees Celsius; and (c) the coolant temperature or oil temperature is 60 degrees Celsius or higher (warm-up state). In these states, the following controls are performed:

(a) When the coolant temperature or oil temperature is lower than 20 degrees Celsius (cold state)
Irrespective of the degree of opening of the accelerator and the number of engine revolutions, valve V1 is opened and valve V2 is fully closed so that only exhaust gas in exhaust extraction route EGR1 is directed to the engine. This is intended to warm up the engine that is in cold state.
(b) When the coolant temperature or oil temperature is 20 degrees Celsius or higher than 20 degrees Celsius and lower than 60 degrees Celsius
Depending on the degree of opening of the accelerator and the number of engine revolutions, the flow rate of each of valves V1 and V2 is controlled.
Specifically, if the degree of opening of the accelerator is at "fully opened", valve V1 is fully closed irrespective of the number of engine revolutions and valve V2 is opened so that only exhaust gas in exhaust extraction route EGR2 is directed to the engine.
If the degree of opening of the accelerator is at "partially opened" and the number of engine revolutions is at the minimum speed or at an intermediate speed, valves V1 and V2 are opened so that both exhaust gas in exhaust extraction route EGR1 and exhaust gas in exhaust extraction route EGR2 are directed to the engine.
If the degree of opening of the accelerator is at "partially opened" and the number of engine revolutions is at the maximum speed, valve V 1 is fully closed and valve V2 is opened so that only exhaust gas in exhaust extraction route EGR2 is directed to the engine.
If the degree of opening of the accelerator is at "fully closed" and the number of engine revolutions is at the minimum speed, valve V 1 is opened and valve V2 is fully closed so that only exhaust gas in exhaust extraction route EGR1 is directed to the engine.
If the degree of opening of the accelerator is at "fully closed" and the number of engine revolutions is at an intermediate speed, valves V1 and V2 are opened so that both exhaust gas in exhaust extraction route EGR1 and exhaust gas in exhaust extraction route EGR2 are directed to the engine.
If the degree of opening of the accelerator is at "fully closed" and the number of engine revolutions is at the maximum speed, valve V 1 is fully closed and valve V2 is opened so that only exhaust gas in exhaust extraction route EGR2 is directed to the engine.
(c) When the coolant temperature or oil temperature is 60 degrees Celsius or higher (warm-up state)

Irrespective of the degree of opening of the accelerator and the number of engine revolutions, valve V1 is fully closed and valve V2 is opened so that only exhaust gas in exhaust extraction route EGR2 is directed to the engine.
It should be noted that, when both exhaust gas in exhaust extraction route EGR 1 and exhaust gas in exhaust extraction route EGR2 are directed to the engine, it is desirable to adjust the blend ratio of exhaust gas from exhaust extraction route EGR 1 to exhaust gas from exhaust extraction route EGR 2 in such a way that the amount of exhaust gas from exhaust extraction route EGR2 increases as the number of engine revolutions increases, or that the amount of exhaust gas from exhaust extraction route EGR 2 increases as the degree of opening of the accelerator increases.
This is intended to adjust the amount of gas from each of the exhaust extraction routes to be mixed in such a way that the intake air temperature in the engine after the mixing is equal to a target intake air temperature. Such adjustments can be performed so that the temperature during fuel combustion lies at 1500-1800 (K), thereby reducing harmful exhaust gas (CO, NOx) or smoke.
During engine start-up, exhaust gas in EGR is used without being cooled. Before engine start-up, there is no combustion within the engine so that exhaust gas contains enough oxygen. Thus, start-up is not adversely affected. Startability is further improved if fuel is not injected during several early cycles.

[Second Embodiment]

Figure 7 shows a configuration of an exhaust gas recirculation device for a two-wheeled motor vehicle according to a second embodiment of the present invention.
The exhaust gas recirculation device according to the present embodiment is different from that of the first embodiment in that another exhaust extraction route EGR3 is provided for mixing exhaust gas immediately after exiting exhaust manifold 109 (immediately after exiting engine 101) with exhaust gas in exhaust extraction route EGR2.
A valve V3 is provided in mid-flow of exhaust extraction route EGR3 for regulating the flow rate of exhaust gas in exhaust extraction route EGR3. It is used for mixing hot EGR gas in exhaust extraction route EGR3 with gas in exhaust extraction route EGR2 to adjust the temperature of the mixture, before it is introduced into the intake.
Figure 8 is a block diagram of a control circuit of the exhaust gas recirculation device of Figure 7.
In addition to the configuration of the control unit shown in Figure 4, engine control unit 201 in the exhaust gas recirculation device further controls valve V3 for regulating the flow rate of exhaust gas in exhaust extraction route EGR3, described above.
Figure 9 illustrates a control method for the valves of the exhaust gas recirculation device according to the second embodiment.
Similar to Figure 6, this figure also shows how engine control unit 201 regulates the degree of opening of valves V1, V2 and V3 based on the degree of opening of the accelerator and the number of engine revolutions in the following conditions: (a) the coolant temperature or oil temperature is lower than 20 degrees Celsius (cold state); (b) the coolant temperature or oil temperature is 20 degrees Celsius or higher than 20 degrees Celsius and lower than 60 degrees Celsius; and (c) the coolant temperature or oil temperature is 60 degrees Celsius or higher (warm-up state). In these states, the following controls are performed:

(a) When the coolant temperature or oil temperature is lower than 20 degrees Celsius (cold state)
Irrespective of the degree of opening of the accelerator and the number of engine revolutions, valve V1 is opened and valves V2 and V3 are fully closed so that only exhaust gas in exhaust extraction route EGR1 is directed to the engine. This is intended to warm up the engine that is in cold state.
(b) When the coolant temperature or oil temperature is 20 degrees Celsius or higher than 20 degrees Celsius and lower than 60 degrees Celsius
Depending on the degree of opening of the accelerator and the number of engine revolutions, the flow rate of each of valves V1, V2 and V3 is controlled.
If the degree of opening of the accelerator is at "fully opened", valves V 1 and V3 are fully closed irrespective of the number of engine revolutions and valve V2 is opened so that only exhaust gas in exhaust extraction route EGR2 is directed to the engine.
If the degree of opening of the accelerator is at "partially opened" and the number of engine revolutions is at the minimum speed or at an intermediate speed, valve V1 is fully closed and valves V2 and V3 are opened so that both exhaust gas in exhaust extraction route EGR2 and exhaust gas in exhaust extraction route EGR3 are directed to the engine.
If the degree of opening of the accelerator is at "partially opened" and the number of engine revolutions is at the maximum speed, valves V 1 and V3 are fully closed and valve V2 is opened so that only exhaust gas in exhaust extraction route EGR2 is directed to the engine.
If the degree of opening of the accelerator is at "fully closed" and the number of engine revolutions is at the minimum speed, valve V1 is opened and valves V2 and V3 are fully closed so that only exhaust gas in exhaust extraction route EGR1 is directed to the engine.
If the degree of opening of the accelerator is at "fully closed" and the number of engine revolutions is at an intermediate speed, valve V 1 is fully closed and valves V2 and V3 are opened so that both exhaust gas in exhaust extraction route EGR2 and exhaust gas in exhaust extraction route EGR3 are directed to the engine.
If the degree of opening of the accelerator is at "fully closed" and the number of engine revolutions is at the maximum speed, valves V1 and V3 are fully closed and valve V2 is opened so that only exhaust gas in exhaust extraction route EGR2 is directed to the engine.
(c) When the coolant temperature or oil temperature is 60 degrees Celsius or higher (warm-up state)

Irrespective of the degree of opening of the accelerator and the number of engine revolutions, valves V1 and V3 are fully closed and valve V2 is opened so that only exhaust gas in exhaust extraction route EGR2 is directed to the engine.
It should be noted that, when both exhaust gas in exhaust extraction route EGR2 and exhaust gas in exhaust extraction route EGR3 are directed to the engine, it is desirable to adjust the blend ratio of exhaust gas from exhaust extraction route EGR2 to exhaust gas from exhaust extraction route EGR3 in such a way that the amount of exhaust gas from exhaust extraction route EGR2 increases as the number of engine revolutions increases, or that the amount of exhaust gas from exhaust extraction route EGR2 increases as the degree of opening of the accelerator increases.
In this embodiment, too, this is intended to adjust the amount of gas from each of the exhaust extraction routes to be mixed in such a way that the intake air temperature in the engine after the mixing is equal to a target intake air temperature. Such adjustments can be performed so that the temperature during fuel combustion lies at 1500-1800 (K), thereby reducing harmful exhaust gas (CO, NOx) or smoke.

[Third Embodiment]

Figure 10 is a side view of a two-wheeled motor vehicle incorporating the exhaust gas recirculation device of Figure 1 according to a third embodiment.
The figure shows an exhaust gas recirculation device incorporated in an off-road two-wheeled motor vehicle.
As shown, EGR cooler 123 is attached to the front part of the body frame. Further, muffler 115 is mounted above back wheel 153.
Exhaust extraction route EGR1 is provided as a route for mixing exhaust gas immediately after exiting engine 101 with intake air for engine 101. Frame 121, forming a portion of exhaust extraction route EGR2, serves as the frame of the two-wheeled motor vehicle, too.
A route 125 is provided in the middle of frame 121 for draining water and soot.
Figure 11 is a side view of a frame 121.
The implementation shown uses a hollow frame 121. In the figure, the route for exhaust gas is indicated by arrows.
Frame 121 includes: an exhaust gas inlet 121a for introducing exhaust gas from muffler 115 into the frame; and an exhaust gas outlet 121 b for directing exhaust gas to EGR cooler 123.
In the case of a cast frame that is not hollow, an exhaust gas passageway made of an SUS (Stainless Steel) pipe(s) can be fixed to the frame, the passageway being in contact with the frame, to provide a route for exhaust gas integrated into the frame.

[Fourth Embodiment]

Figure 12 is a side view of a two-wheeled motor vehicle incorporating the exhaust gas recirculation device of Figure 1 according to a fourth embodiment.
The present implementation shows an exhaust gas recirculation device incorporated into a naked two-wheeled motor vehicle.
As shown, EGR cooler 123 is attached to the front part of the body frame. Further, muffler 115 is mounted close to the side of back wheel 153.
Exhaust extraction route EGR1 is provided as a route for mixing exhaust gas immediately after exiting engine 101 with intake air for engine 101. Frame 121, forming a portion of exhaust extraction route EGR2, serves as the frame of the two-wheeled motor vehicle, too.
Further, a route 125 is provided in the middle of frame 121 for draining water and soot.
Figure 13 is a side view of a frame 121.
The implementation shown uses a hollow frame 121. In the figure, the route for exhaust gas is indicated by arrows.
Frame 121 includes: an exhaust gas inlet 121a for introducing exhaust gas from exhaust pipe 113 disposed upstream of muffler 115 into the frame; and an exhaust gas outlet 121b for directing exhaust gas to EGR cooler 123.
In the case of a cast frame that is not hollow, an exhaust gas passageway made of an SUS (Stainless Steel) pipe(s) can be fixed to the frame, the passageway being in contact with the frame, to provide a route for exhaust gas integrated into the frame.

[Effects of Embodiments]

According to the above embodiments, hot exhaust gas immediately after the exhaust valve can be used for EGR when the temperature of intake air for the engine is to be increased during start-up, during warm-up operation or the like. Thus, increase in temperature in the cylinder(s) can be promoted to ensure stable engine start-up.
Furthermore, during high load operation while the vehicle is running, the temperature of exhaust gas used for EGR should be as low as possible in order to reduce NOx and fuel consumption. In the various embodiments, while the vehicle is running, exhaust gas that has been sufficiently cooled by passing through the exhaust pipe and the like can be introduced into EGR.
Further, during low to middle load operations, two EGR routes can be combined to achieve an exhaust gas temperature equal to a target temperature before exhaust gas is introduced into the intake. Thus, the amount of smoke emission can be reduced.
Exhaust gas from the engine can be cooled using at least one of the following: the turbocharger, the muffler, the frame of the vehicle, and a pipe attached to the frame. In this way, exhaust gas can be efficiently cooled.
Moreover, the use of exhaust gas that has been cooled in such a way reduces the load on the EGR cooler, thereby allowing a smaller EGR cooler to be used (or eliminates the necessity for an EGR cooler).
Furthermore, by using the body frame as a portion of the EGR route(s), the number of components of the EGR piping can be reduced.
Further, exhaust gas that has passed through the muffler can be directed through the body frame to cause heat dissipation with ambient air so that exhaust gas that has been significantly cooled at the muffler can be further cooled.
Also, in mid-flow of the exhaust gas passageway integrated into the body frame, room can be provided at the lowest point to accumulate soot and condensed water, and accumulated matters can be drained naturally through a communicating hole to the outside, thereby ensuring clearance of the passageway.
Moreover, hot EGR gas can be introduced into the engine intake for some time period immediately after engine start-up, thereby reducing smoke.

[Others]

When the number of revolutions of the crank is at a predetermined level or lower during engine start-up, fuel may not be injected and only air may be compressed, and air that has been compressed and become hot may be directed through an EGR route and introduced back into the cylinder.
During engine start-up, fuel injection may be initiated when the number of revolutions of the crank is at a predetermined level or higher. This will ensure more stable startability since the temperature within the cylinder(s) is high at the time of initiation of injection.
The EGR cooler is desirably disposed in the front part of the body or in a place near the engine that receives the wind generated while the vehicle is running, i.e. a location where the wind generated while the vehicle is running can be utilized for cooling.
No EGR cooler has to be used at all if exhaust gas can be sufficiently cooled in the EGR route(s).
Further, exhaust gas extracted immediately after the exhaust valve (upstream of the turbocharger, i.e. a high pressure section) is desirably introduced into a section immediately prior to the intake valve (a high pressure section). Also, exhaust gas that has been extracted from the muffler or the like (downstream of the turbo, a low pressure section) and cooled is desirably introduced into a section upstream of the compressor (a low pressure section). This is intended to make the pressure at one end of an EGR route close to that of its other end, thereby facilitating adjustment of pressures.
While examples with a small chamber disposed in mid-flow of an exhaust gas passageway including a body frame were described, a small chamber may be replaced by a filter structure with a labyrinthine configuration for gathering soot and condensed water. Alternatively, a portion in mid-flow of the passageway may be in a T-shape where water and soot can be trapped in the lower portion.
The present invention can be employed for both an engine with a turbocharger and an engine without a turbocharger. The engine may be a diesel or gasoline engine.
The present invention can be employed for two-wheeled motor vehicles and saddle type vehicles such as motor-assisted bicycles. The present invention may be carried out in any saddle type vehicle, such as two-wheeled, three-wheeled or four-wheeled vehicles (or vehicles with more wheels), or vehicles that can be moved using a crawler mechanism. Further, the present invention may be employed in automobiles and other vehicles with an engine.
It should be understood that the above embodiments are exemplary only and not restrictive in any way. The scope of the present invention is indicated not by the above description but by the Claims, and all the modifications equivalent to and within the Claims are intended to be included.

Claims

An exhaust gas recirculation device including an exhaust extraction route (EGR2) for extracting exhaust gas from an engine (101) and directing it to an intake (111) of the engine, characterized in that
said exhaust extraction route (EGR2) includes a route for cooling exhaust gas from the engine (101) by directing it through a frame (121) of a vehicle or through a pipe attached to a frame (121).
The exhaust gas recirculation device according to claim 1, characterized in that
said exhaust extraction route (EGR2) is a low temperature exhaust extraction route for extracting exhaust gas after it has exited a turbocharger (103a) and directing it to the engine intake (111), and further characterized by:
a high temperature exhaust extraction route (EGR1) for extracting exhaust gas from the engine (101) before it enters said turbocharger (103a) and directing it to the engine intake (111); and

a control means (201, V1, V2) for controlling, based on operation conditions (203-211) of the engine, a flow of exhaust gas to be directed to the engine intake (111) by means of said high temperature exhaust extraction route (EGR1) and said low temperature exhaust extraction route (EGR2).
The exhaust gas recirculation device according to claim 2, characterized in that
said low temperature exhaust extraction route (EGR2) directs exhaust gas from the engine (101) to an upstream of a compressor (103b) of said turbocharger, and
said high temperature exhaust extraction route (EGR1) directs exhaust gas from the engine (101) to a downstream of the compressor (103b) of said turbocharger.
The exhaust gas recirculation device according to claim 1, characterized by
a high temperature exhaust extraction route (EGR1) for extracting exhaust gas from the engine (101) before it enters a muffler (115) and directing it to the engine intake (111), and further characterized in that
said exhaust extraction route (EGR2) is a low temperature exhaust extraction route for extracting exhaust gas from the engine (101) downstream of an extraction location of said high temperature exhaust extraction route (EGR1) and directing it to the engine intake (111), and further characterized by
a control means (201, V1, V2) for controlling, based on operation conditions (203-211) of the engine, a flow of exhaust gas to be directed to the engine intake (111) by means of said high temperature exhaust extraction route (EGR1) and said low temperature exhaust extraction route (EGR2).
The exhaust gas recirculation device according to claim 4, characterized in that
said low temperature exhaust extraction route (EGR2) is an exhaust extraction route for extracting exhaust gas that has passed through said muffler (115) and directing it to the engine intake (111).
The exhaust gas recirculation device according to any one of claims 2 to 5, characterized by
a mixing exhaust extraction route (EGR3) for mixing exhaust gas passing through said high temperature exhaust extraction route (EGR1) with exhaust gas passing through said low temperature exhaust extraction route (EGR2), and further characterized in that
said control means (201, V1, V2, V3) controls, based on operation conditions (203-211) of the engine, a flow of exhaust gas in said mixing exhaust extraction route.
A vehicle including an engine, characterized by
the exhaust gas recirculation device according to any one of the preceding claims connected with said engine.